1. Technical Field
The disclosure relates generally to integrated circuits (ICs), and more particularly, to an IC interconnect for high current.
2. Background Art
Back-end-of-line (BEOL) interconnects carry high direct current (DC) in advanced integrated circuit (IC) chip technology. As IC chip technology advances, self-heating by high current devices raises the temperature of nearby interconnects under circuit operation and makes use of high current carrying BEOL interconnects more challenging. For example, a device that uses high current and self-heats (e.g., a resistor, transistor, etc.) may heat up an interconnect that couples to the device. The high current leads to electromigration degradation of the interconnect (via and/or line), causing shorts or opens. As a result, the current-carrying capability (or the Idc limit specified in the design manuals) is significantly reduced to avoid electromigration degradation in interconnects. As an example, a direct current limit in a copper interconnect may be reduced by a factor of more than 3, resulting from a temperature rise of 15° C. from, for example, 85° C. to 100° C., and by almost a factor of 20 at a 125° C. interconnect temperature. As a result, high direct current at elevated temperatures is almost impossible with conventional interconnect wiring design.
Conventionally, the above-described situation is circumvented simply by widening the interconnect that is carrying the high current. However, this solution is hindered because of severe current crowding at the via/line contact interface, which is very susceptible to electromigration damage. In particular, the field distribution near the end of the metal line is typically not uniform, resulting in significant current crowding which is the main reason for causing electromigration degradation in interconnects.